The present invention relates generally to superconductivity, and more particularly to a superconductive rotor for synchronous electrical machines.
Synchronous electrical machines having rotors include, but are not limited to, generators and motors. Non-superconducting rotors include solid-core rotors, such as iron-core rotors. Iron-core rotors saturate at an air-gap magnetic field strength of about 2 Tesla. Known superconductive rotors employ air-core designs to achieve air-gap magnetic fields of 3 Tesla or higher. Air-core superconductive rotors require large amounts of superconductive wire which adds to the number of coils required, the complexity of the coil supports, and the cost. Such superconductive rotors have their superconductive coils cooled by liquid helium, with the used helium being returned as room-temperature gaseous helium. Using liquid helium for cryogenic cooling requires continuous reliquefaction of the returned, room-temperature gaseous helium, and such reliquefaction poses significant reliability problems and requires significant additional energy. What is needed is a superconductive rotor, for an air-gap magnetic field strength of about 2 Tesla or less, that does not have the disadvantages of the air-core and liquid-cooled superconductive rotors.